I take it you refer to the likes of Webley and Scott . Where parts were machined to within a set tolerance then hand filed and fitted . The whole thing being filed up by hand so that the individual crafts man "left his imprint" .
I doubt very strongly that any gun making has taken place since the advent of the breech loader that has not been of this type. Even in the percussion days Lock parts were either forged or partially machined ,then filed up in a jig often I understand by the apprentices before assembly by the "masters".